The superior olivary complex (SOC) contains the cells of origin of fibers ascending within the lateral lemniscus, of afferent fibers participating within the middle ear reflex paths, of efferent axons that terminate within the cochlear nuclear complex and of fibers in the olivocochlear bundle that terminate within the cochlea. The SOC is believed to be the first stage within the ascending auditory pathway to play a major role in the processing of binaural information. The proposed studies represent a continuation of a long-term research project involved in describing the functional cell groups of the SOC. The objectives of the project are: (1) to specify electrophysiologically the response characteristics of SOC neurons and to identify and characterize the SOC neurons on the basis of these response measures; (2) to determine the manner in which auditory information is encoded by SOC neurons by utilizing the theory of point processes as the mathematical framework of the representation of sensory information in neural discharge patterns; (3) to examine the response properties of SOC neurons believed to function within the efferent and motor-reflex systems; and (4) ultimately, to relate the response properties of the SOC neurons to their morphology and to the neural inputs provided by the cochlear nuclear complex. The single unit activity is elicited by click, tone and white noise stimuli. The location of the units studied are determined histologically so that the characteristics of morphologically different cell groups can be compared. With the aid of the computer, standard spike generated histograms and statistical measures are utilized to describe the discharges elicited from single neurons under monaural and binaural stimulus conditions. The results of the computer analyses of single unit spike train data serve as a basis for classifying units and for describing the population response in terms of the discharges of single neurons.